Getting disconnected when adding a VLAN interface

I am trying to configure an SF302-08MP switch in a test environment with a couple of VLANs. From a default state I have configured the unit to be in L3 mode, added a VLAN then added an IP interface for that VLAN. The problem I have is that as soon as I add the IP interface for the VLAN I create I immediately lose connection to the switch and either have to reconfigure the interface via the CLI or reboot the unit to lose my changes.

I realise I can configure the box via the CLI to regain my connection and complete the configuration for my VLANs, but I'm trying to get a good process down for configuring these all via the web interface (apart from the initial L3 mode setup of course).

For this I am connecting to the default IP address on VLAN 1 (192.168.1.254). The steps taken are as follows:

In addition to the above I've just performed a 'show ip interface vlan x' command before and after my changes within the web config and it appears that the switch is dropping its VLAN1 IP address once a new interface is added: